Sequential Phase‐Engineered Afterglow Modulation in Mn‐Doped Cs‐Cd‐Cl Perovskites for X‐ray Time‐Lapse Flexible Imaging

X-ray time-lapse flexible imaging and information retrieval significantly broaden the application scope of X-ray technologies, while posing new challenges for the design of advanced scintillators. Herein, we report a phase transition-guided strategy for the rational design of Mn-doped ternary cadmium chlorides long afterglow emitters, wherein crystal growth dynamics are precisely modulated via solubility-controlled synthesis. By sequentially preparing powders and single crystals of Cs₂CdCl₄:Mn, Cs₃Cd₂Cl₇:Mn, and CsCdCl₃:Mn, we achieve phase-selective synthesis through fine-tuning of mixed solvent ratios, establishing a robust framework for phase engineering in the Mn-doped Cs-Cd-Cl system. Among them, CsCdCl₃:Mn exhibits the highest trap density, resulting in a pronounced scintillation afterglow. Benefiting from this unique property, a flexible scintillating film fabricated by embedding phosphor powders into a polymer matrix enables high-resolution time-lapse X-ray imaging (13.6 lp mm^-1), along with thermally stimulated image retrieval after X-ray exposure. This work not only presents a generalizable approach for phase-controlled afterglow modulation in Mn-doped chlorides, but also offers new avenues toward flexible, high-performance X-ray scintillators with delayed visualization capabilities.